Packing machine and method and device for controlling cigarette tips

ABSTRACT

A method and device for controlling tips of cigarettes fed in groups along a feed path through a control station; the device has a number of sensors, each of which induces a stationary microwave field to determine correct fill of the tips of cigarettes travelling through the stationary microwave field.

The present invention relates to a packing machine and to a method and device for controlling cigarette tips.

BACKGROUND OF THE INVENTION

On cigarette packing machines, the tips of cigarettes in a group are analyzed to ensure they are filled.

More specifically, this is done by light scattering analysis of the cigarette tips. Devices employing this type of analysis comprise a source for emitting a light beam substantially parallel to the axis of a cigarette for analysis; and sensors positioned crosswise to the cigarette to detect scattered light. As described in U.S. Pat. No. 4,907,607, to perform this type of analysis correctly on groups of cigarettes, the individual cigarettes must be offset with respect to the groups, so that the sensors are positioned correctly about the cigarettes. This complicates the packing machine (devices must be provided to offset and re-position the cigarettes) and increases the risk of damaging the cigarettes.

To check filling of cigarette tips, back scattering analysis has also been proposed, and which comprises directing a light beam, parallel to the cigarette axis, onto the tip of the cigarette, and determining the light scattered in the direction of the beam. Back scattering has the disadvantage that, in the event the cigarette tip is filled on the surface but with a void at the back, the light is still detected and the cigarette tip therefore considered properly filled.

Another important point to note is that both scattering and back scattering analysis also have the drawback of the detected data depending on the colour of the tobacco. Which means a change in tobacco colour involves recalibrating the sensors, thus increasing running cost and downtime.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a packing machine and a method and device for controlling the fill of cigarette tips, designed to eliminate the aforementioned drawbacks, and which, in particular, are cheap and easy to implement.

According to the present invention, there is provided a device and a method for controlling the fill of cigarette tips and a packing machine, as claimed in the attached Claims.

BRIEF DESCRIPTION OF THE DRAWINGS

A number of non-limiting embodiments of the present invention will be described by way of example with reference to the accompanying drawings, in which:

FIG. 1 shows a schematic front view of a cigarette packing machine in accordance with the present invention;

FIG. 2 shows a larger-scale detail of the FIG. 1 machine;

FIG. 3 shows a section of a larger-scale detail of the FIG. 2 detail;

FIG. 4 shows a graph of test data acquired in accordance with the present invention; the x axis shows frequency in GHz, and the y axis the power measurement;

FIG. 5 shows a graph of test data acquired in accordance with the present invention; the x axis shows frequency deviations in GHz, and the y axis power measurement deviations;

FIG. 6 shows a further embodiment of the FIG. 3 detail;

FIG. 7 shows a cross section of the FIG. 6 detail;

FIG. 8 shows a section of a further embodiment of the FIG. 3 detail;

FIG. 9 shows straight lines obtained by linear interpolation of test data obtained measuring tobacco of known density and humidity; the x axis shows the A_(Δ)/A_(i) ratio, and the y axis density.

DETAILED DESCRIPTION OF THE INVENTION

Number 1 in FIG. 1 indicates as a whole a packing machine for producing packets of cigarettes. Packing machine 1 comprises a device 2 (FIG. 2) for controlling the fill of tips 3 of cigarettes 4. Device 2 is located downstream from a hopper 5 (shown schematically in FIG. 1) for cigarettes 4, and upstream from a reject unit (not shown), and in turn comprises a conveyor 6 for feeding groups 7 of cigarettes 4, crosswise to cigarettes 4, along a feed path P through a control station 8 equipped with a control unit 9.

Conveyor 6 comprises a belt 10; and a number of seats 11, each for housing a respective group 7 of cigarettes 4 comprising three superimposed rows 12 of cigarettes 4.

Control unit 9 comprises a number of—in particular, three—microwave sensors 13 arranged one on top of another, so that, as group 7 of cigarettes 4 travels through control station 8, each sensor 13 detects the density of the tips of cigarettes 4 in a respective row 12.

In the FIG. 3 embodiment, each sensor 13 produces a respective stationary microwave field 14 of given shape, and emits a number of acquisition signals, each depending on the density of a respective tip 3 of cigarette 4 travelling through microwave field 14. More specifically, microwave field 14 is substantially hemispherical.

Each sensor 13 comprises a body 15 made of conducting material (e.g. aluminium) and having a substantially circular groove 16 defining a flat member 17 coated externally with two layers 17′ and 18 of dielectric material (e.g. alumina or plastic), and a further layer 19 of conducting material. Layer 17′ directly contacts flat member 17, and is located on the opposite side of layer 19 to layer 18. Flat member 17 is typically about 8 mm in diameter.

Each sensor 13 also comprises two electrodes 20 for connecting layer 17′ of dielectric material to a generator 21 and to a detector (not shown) of a computer 22 respectively.

In actual use, as a group 7 of cigarettes 4 travels through control station 8, each sensor 13 emits a detection signal for each cigarette 4 whose tip 3 travels through the respective microwave field 14. At this point, computer 22 compares the detection signal with a reference data item. More specifically, computer 22 determines a detection data item as a function of the detection signal, and compares the detection data item with the reference data item. If the difference between the detection signal and the reference data item exceeds a given threshold value, an error signal indicating a faulty cigarette 4 is emitted. In which case, the reject unit (not shown) downstream from device 1 and connected to computer 22 eliminates the faulty cigarette 4 or (in other embodiments) the group 7 containing the faulty cigarette 4.

Operation of sensor 13 and computer 22 will now be explained in more detail with particular reference to FIGS. 4 and 5. For each measurement, sensor 13 performs a sweep to vary the microwave frequency in microwave field 14 between 1 GHz and 300 GHz. Microwave frequency is preferably varied between 2 and 3 GHz to avoid heating the tobacco in cigarettes 4 travelling through control station 8 and/or any biological tissue in microwave field 14.

FIG. 4—in which the y axis shows microwave frequency, and the x axis the power measurement—shows a reference curve C_(R) relative to a reference signal obtained with substantially no objects in microwave field 14. Reference curve C_(R) has a peak at a given reference frequency A_(R), and a reference amplitude B_(R) at mid peak height.

FIG. 4 also shows response curves C_(i), C_(ii), C_(iii) of relative detection signals. Each response curve has a relative peak detected frequency A_(i), and a relative detected amplitude B_(i) at mid peak height; which peak detected frequency A_(i) and detected amplitude B_(i) depend on the humidity and density of a tip 3 of analyzed cigarette 4.

In actual use, to determine the fill of tip 3 of cigarette 4, computer 22 receives the detection signal, and determines peak detected frequency A_(i) and detected amplitude B_(i), which are then processed to permit a comparison between the detection signal and the reference data item.

Computer 22 preferably determines a first deviation A_(Δ) between peak detected frequency A_(i) and reference frequency A_(R), and a second deviation B_(Δ) between detected amplitude B_(i) and reference amplitude B_(R). At this point, a detected humidity of tip 3 of cigarette 4 is determined, in particular by means of the following equation: $\varphi = {{arctg}\quad\frac{A_{\Delta}}{B_{\Delta}}}$ where φ is directly proportional to detected humidity. In this connection, it should be pointed out that, in a test graph showing first deviation A_(Δ) along the x axis, and second deviation B_(Δ) along the y axis (as in FIG. 5), the points relative to detection signals of tips 3 of different cigarettes 4 of substantially the same humidity substantially lie on the same straight lines.

Given the detected humidity, computer 22 determines a detected density of tip 3 of cigarette 4 as a function of detected humidity and of first deviation A_(Δ) or second deviation B_(Δ). More specifically, density is calculated using curves (in particular, straight lines) T determined beforehand experimentally (and shown in FIG. 9). Each curve T defines density (indicated ρ in FIG. 9) as a function of ratio A_(Δ)/A_(i) at a given constant humidity (i.e. a given constant φ).

At this point, the detected density (i.e. the detected data item) is compared with a reference density (i.e. the reference data item); and, if the difference between the detected density and the reference density exceeds the threshold value, the error signal is emitted.

In a further embodiment shown in FIGS. 6 and 7, sensor 13 comprises a flat circular body 23 of dielectric material (e.g. alumina) coated with a layer 24 of conducting material (e.g. copper) having a number of circular holes 25. In this case, microwave field 14 is substantially cylindrical.

In a further embodiment shown in FIG. 8, sensor 13 comprises a body 26 of dielectric material (e.g. alumina) coated with a layer 27 of conducting material (e.g. copper) having three circular holes 28, and three substantially parallelepiped-shaped members 29 of conducting material; and holes 28 are covered with a layer of insulating material 30. In this case, sensor 13 defines three microwave fields 14, and therefore controls the mean density of three tips 3 of cigarettes 4 simultaneously.

Device 1 has the following advantages:

-   -   cigarettes 4 need not be offset with respect to one another;     -   detection signals, and therefore density measurements,         independent of tobacco colour are obtained;     -   detection signals, and therefore density measurements, sensitive         to below-surface tobacco voids are obtained. 

1) A device for controlling the fill of cigarette tips, comprising conveying means (6) for feeding a group (7) of cigarettes (4) along a feed path (P) through a control station (8); at least one sensor (13) located at the control station (8), and which emits a detection signal as a function of the fill of a tip (3) of a cigarette (4); and a computer (22) connected to the sensor (13), and which compares the detection signal with a reference data item, and emits an error signal as a function of the comparison between the reference data item and the detection signal; the device being characterized in that the sensor (13) comprises a microwave sensor (13) for producing a microwave field (14) of a substantially given shape, and through which the tip (3) of the cigarette (4) travels in use; the detection signal being a function of the density of the tip (3) of the cigarette (4). 2) A device as claimed in claim 1, wherein the computer (22) determines a detection data item as a function of the detection signal, and emits the error signal when the difference between the detection data item and the reference data item exceeds a threshold value. 3) A device as claimed in claim 1, wherein the microwave sensor (13) defines a planar microwave field (14). 4) A device as claimed in claim 1, wherein the conveying means (6) convey the groups (7) of cigarettes (4) crosswise to the cigarettes (4). 5) A device as claimed in claim 1, wherein the sensor (13) emits a respective detection signal for each cigarette (4) whose tip (3) travels through the microwave field (14). 6) A device as claimed in claim 1, and comprising at least three sensors (13), each for controlling tips (3) of cigarettes (4) in a respective row (12) of cigarettes (4) in each group (7) of cigarettes (4); each group (7) of cigarettes (4) comprising three superimposed rows (12) of cigarettes (4). 7) A device as claimed in claim 1, wherein the detection signal comprises a response curve (C_(i), C_(ii), C_(iii)) having a peak detected frequency (A_(i)), and a detected amplitude (B_(i)) at mid peak height; the peak detected frequency (A_(i)) and the detected amplitude (B_(i)) being functions of the density and humidity of the tip (3) of the cigarette (4); and the computer (22) comparing the detection signal with the reference data item by processing the peak detected frequency (A_(i)) and the detected amplitude (B_(i)). 8) A device as claimed in claim 7, wherein the computer (22) determines a detected density of the tip (3) of the cigarette (4) as a function of the peak detected frequency (A_(i)) and the detected amplitude (B_(i)). 9) A device as claimed in claim 8, wherein the computer (22) determines a detected humidity of the tip (3) of the cigarette (4) as a function of the peak detected frequency (A_(i)) and the detected amplitude (B_(i)), and determines the detected density as a function of the detected humidity and the peak detected frequency (A_(i)) or the detected amplitude (B_(i)). 10) A device as claimed in claim 7, wherein the computer (22) determines a first deviation (A_(Δ)) between the peak detected frequency (A_(i)) and a reference frequency (A_(R)), determines a second deviation (B_(Δ)) between the detected amplitude (B_(i)) and a reference amplitude (B_(R)), and determines a detected humidity of the tip (3) of the cigarette (4) as a function of the first and second deviation (A_(Δ), B_(Δ)); the reference frequency (A_(R)) and the reference amplitude (B_(R)) being the peak frequency and mid-peak-height amplitude respectively of a reference curve (C_(R)) of a reference signal obtained with substantially no objects in the microwave field (14). 11) A device as claimed in claim 10, wherein the computer (22) determines a detected humidity of the tip (3) of the cigarette (4) as a function of the first and second deviation (A_(Δ), B_(Δ)), and determines the detected density as a function of the detected humidity and the first or second deviation (A_(Δ), B_(Δ)) . 12) A device as claimed in claim 11, wherein the computer (22) determines the detected humidity of the tip (3) of the cigarette (4) according to the following equation: $\varphi = {{arctg}\quad\frac{A_{\Delta}}{B_{\Delta}}}$ where φ is directly proportional to the detected humidity, A_(Δ) indicates the modulus of the first deviation, and B_(Δ) indicates the modulus of the second deviation. 13) A device as claimed in claim 12, wherein the computer (22) determines the detected density of the tip (3) of the cigarette (4) using test curves (T), each of which is predetermined experimentally at a respective given constant humidity; and each curve (T) describes the density pattern as a function of the ratio A_(Δ)/A_(i). 14) A device as claimed in claim 1, wherein the computer (22) breaks the detection signal down into two components (A_(i), B_(i)), each of which is a function of the humidity and density of the tip (3) of the cigarette (4); determines the detected humidity as a function of the two components (A_(i), B_(i)); and determines the detected density as a function of the detected humidity and at least one of the two components (A_(i), B_(i)). 15) A method of controlling the fill of cigarette tips, the method comprising conveying a group (7) of cigarettes (4) along a feed path (P) through a control station (8); determining a detection signal as a function of the fill of a single tip (3) of a cigarette (4); and comparing the detection signal with a reference data item, and emitting an error signal as a function of the comparison between the detection signal and the reference data item; the method being characterized in that the detection signal is determined by producing a microwave field (14) of substantially given shape, through which microwave field (14) the tip (3) of the cigarette (4) travels; the detection signal being a function of the density of the tip (3) of the cigarette (4). 16) A method as claimed in claim 15, wherein an error signal is emitted when the difference between a detection data item, determined as a function of the detection signal, and the reference data item exceeds a threshold value. 17) A method as claimed in claim 15, wherein the microwave field (14) is a planar microwave field (14). 18) A method as claimed in claim 15, wherein the cigarettes (4) are conveyed transversely through the control station (8). 19) A method as claimed in claim 15, wherein the detection signal comprises a response curve (C_(i), C_(ii), C_(iii)) having a peak detected frequency (A_(i)), and a detected amplitude (B_(i)) at mid peak height; the peak detected frequency (A_(i)) and the detected amplitude (B_(i)) being functions of the density and humidity of the tip (3) of the cigarette (4); and the detection signal being compared with the reference data item by processing the peak detected frequency (A_(i)) and the detected amplitude (B_(i)). 20) A method as claimed in claim 19, wherein a detected density of the tip (3) of the cigarette (4) is determined as a function of the peak detected frequency (A_(i)) and the detected amplitude (B_(i)). 21) A method as claimed in claim 20, wherein a detected humidity of the tip (3) of the cigarette (4) is determined as a function of the peak detected frequency (A_(i)) and the detected amplitude (B_(i)); the detected density being determined as a function of the detected humidity and the peak detected frequency (A_(i)) or the detected amplitude (B_(i)). 22) A method as claimed in claim 20, wherein a first deviation (A_(Δ)) between the peak detected frequency (A_(i)) and a reference frequency (A_(R)) is determined; a second deviation (B_(Δ)) between the detected amplitude (B_(i)) and a reference amplitude (B_(R)) is determined; and the detected density of the tip (3) of the cigarette (4) is determined as a function of the first and second deviation (A_(Δ), B_(Δ)); the reference frequency (A_(R)) and the reference amplitude (B_(R)) being the peak frequency and mid-peak-height amplitude respectively of a reference curve (C_(R)) of a reference signal obtained with substantially no objects in the microwave field (14). 23) A method as claimed in claim 22, wherein the detected humidity of the tip (3) of the cigarette (4) is determined as a function of the first and second deviation (A_(Δ), B_(Δ)), and the detected density is determined as a function of the detected humidity and the first or second deviation (A_(Δ), B_(Δ)). 24) A method as claimed in claim 23, wherein the detected humidity of the tip (3) of the cigarette (4) is determined according to the following equation: $\varphi = {{arctg}\quad\frac{A_{\Delta}}{B_{\Delta}}}$ where φ is directly proportional to the detected humidity, A_(Δ) indicates the modulus of the first deviation, and B_(Δ) indicates the modulus of the second deviation. 25) A method as claimed in claim 23, wherein the detected density of the tip (3) of the cigarette (4) is determined using test curves (T), each of which is predetermined experimentally at a respective given constant humidity; and each curve (T) describes the density pattern as a function of the ratio A_(Δ)/A_(i). 26) A method as claimed in claim 20, wherein the detected density is compared with the reference data item. 27) A method as claimed in claim 26, wherein an error signal is emitted when the difference between the detected density and the reference data item exceeds a threshold value. 28) A method as claimed in claim 15, wherein the detection signal is broken down into two components (A_(i), B_(i)), each of which is a function of the humidity and density of the tip (3) of the cigarette (4); the detected humidity is determined as a function of the two components (A_(i), B_(i)); and the detected density is determined as a function of the detected humidity and at least one of the two components (A_(i), B_(i)). 29) A packing machine comprising a device (1) for controlling the fill of tips (3) of cigarettes (4), as claimed in claim
 1. 